The procedures are, for example, procedures to be carried out before a flight, to check proper operation of the various systems of the aircraft, navigation procedures to be implemented during flight, for example when changing a flight phase, or malfunction procedures to be implemented in the event of failures of one or more pieces of aircraft equipment.
Generally each procedure involves a series of operations defined by the manufacturer and/or the operator, and which are generally validated by certification authorities. These procedures are linked in the form of lists.
The operations are, for example, actions to be performed, such as commands intended for an airplane system, with acknowledgement of their application, questions to the crew requiring a simple response, or requests for crew actions. Other operations are purely for information, such as sending messages and/or information to the crew without a response being expected.
When a procedure is implemented during flight, the crew performs the actions required by actuating the controls positioned in the cockpit, either directly by means of switches or through computers and software controlled by the crew.
In traditional flight with a crew of two, the first member of the crew takes care of the short-term flight and a second crew member successively performs the various actions of the procedure under the control of the first crew member for major or irreversible actions, such as an engine failure, extinction of a fire . . . .
The procedures are generally listed in one or more aircraft operating manuals which are available in paper form or electronically. A large number of procedures are certified and must be strictly applied by the crew, especially in the event of malfunctions.
On modern aircraft, the procedures are stored as computer files in a database and may be displayed on a screen in the cockpit when they have to be implemented.
Generally, the operations of the procedure are successively displayed by a display and validation module, wherein the crew must validate the actions as they are gradually performed.
In some cases, especially in the event of multiple malfunctions on the aircraft, several different procedures must be implemented one after the other.
Generally, the crew determines the order of performing of the procedures by determining which are the most critical. Then, the crew successively executes the various procedures to be implemented by carrying out the provided actions of each procedure one by one.
Furthermore, for safety reasons, particularly in the context of multiple malfunctions, the crew must continually analyze whether the action to be performed of a specific procedure is appropriate with respect to the current operational state of the aircraft. In particular, if the action to be performed might result in a change of state of a piece of equipment of the aircraft, this change of state might affect the appropriate flying of the aircraft, or even the safety of the flight depending on the elements affected by other procedures or by other malfunctions.
By the term <<change of state>> of a piece of equipment, is meant the change from a state of power on to a state of power off or vice versa, the change from an operational state to a state of malfunction, the change of an equipment control mode, or even any change in the positioning of a piece of equipment to a state which is distinctly different from the previous state (e.g. a slat or flap position, or raising/lowering the landing gear).
The crew workload is thus very high, insofar that the crew has to keep the aircraft in flight while carrying out a large number of actions relating to procedures, determining the preferential order for performing the procedures, and the impact of each action of a procedure on the course of the flight.